Optical molding apparatus and optical molding method

ABSTRACT

An optical molding apparatus that molds a three-dimensional model by stacking cured layers. Each cured layer is formed by emitting light according to cross-sectional-shape data of the three-dimensional model onto a surface of photo-curable resin. The optical molding apparatus includes a container that contains the photo-curable resin, a movable stage that is movable in a direction orthogonal to the surface of the photo-curable resin, an optical system that emits the light onto the surface of the photo-curable resin contained in the container so as to form each cured layer on the movable stage, and a discharging mechanism that performs a discharging operation for discharging new photo-curable resin onto a surface of each cured layer formed on the movable stage before stacking a subsequent cured layer.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/354,396, filed Jan. 15, 2009, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims priority to Japanese Patent Application JP2008-010082 filed in the Japanese Patent Office on Jan. 21, 2008, theentirety of which is also incorporated by reference herein to the extentpermitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical molding apparatuses and opticalmolding methods, and particularly, to an optical molding apparatus andan optical molding method that can mold a higher-precisionthree-dimensional model.

2. Description of the Related Art

An optical molding apparatus optically molds a three-dimensional modelby stacking cured layers one of top of the other. Specifically, each ofthese cured layers is formed by emitting light according to one ofcross-sectional-shape data items that corresponds to that cured layeronto a surface of photo-curable resin. These cross-sectional-shape dataitems are obtained by cross-sectionally slicing the three-dimensionalmodel into three-dimensional segments with a predetermined thickness inthe stacking direction.

In optical molding, the presence of small uncured or semi-curedphoto-curable resin (to be described later in detail) in the order ofmicrometers, which is within a permissible error range in related art,becomes non-negligible as the three-dimensional model becomes moredetailed.

In order to improve the precision of a three-dimensional model, JapaneseUnexamined Patent Application Publication Nos. 2007-291393 and2007-76090, for example, suggest removal of uncured photo-curable resinremaining on the surface of a molded three-dimensional model. The term“uncured photo-curable resin” refers to photo-curable resin havingundergone exposure, which is not semi-cured but may possibly becomesemi-cured.

SUMMARY OF THE INVENTION

However, uncured or semi-cured photo-curable resin is created every timeone cured layer is formed. For this reason, when a cured layer isstacked on the previous cured layer having uncured or semi-curedphoto-curable resin remaining thereon, it is difficult to sufficientlyimprove the precision of the three-dimensional model.

It is therefore desirable to achieve the capability to moldhigher-precision three-dimensional models.

According to an embodiment of the present invention, there is providedan optical molding apparatus that molds a three-dimensional model bystacking cured layers. Each cured layer is formed by emitting lightaccording to cross-sectional-shape data of the three-dimensional modelonto a surface of photo-curable resin. The optical molding apparatusincludes a container that contains the photo-curable resin, a movablestage that is movable in a direction orthogonal to the surface of thephoto-curable resin, an optical system that emits the light onto thesurface of the photo-curable resin contained in the container so as toform each cured layer on the movable stage, and a discharging mechanismthat performs a discharging operation for discharging new photo-curableresin onto a surface of each cured layer formed on the movable stagebefore stacking a subsequent cured layer.

The optical molding apparatus according to the aforementioned embodimentof the present invention may further include a vibrating mechanism thatultrasonically vibrates the movable stage during the dischargingoperation performed by the discharging mechanism.

The optical molding apparatus according to the aforementioned embodimentof the present invention may further include a temperature adjustingmechanism that increases or decreases a temperature at an end of thecontainer during the discharging operation performed by the dischargingmechanism so as to create a convection current in the photo-curableresin contained in the container.

The optical molding apparatus according to the aforementioned embodimentof the present invention may further include a renewing mechanism thatrenews the photo-curable resin contained in the container beforestacking the subsequent cured layer.

According to another embodiment of the present invention, there isprovided an optical molding method performed by an optical moldingapparatus that molds a three-dimensional model by stacking cured layers.Each cured layer is formed by emitting light according tocross-sectional-shape data of the three-dimensional model onto a surfaceof photo-curable resin. The optical molding method includes the steps ofemitting the light onto the surface of the photo-curable resin containedin a container so as to form each cured layer on a movable stage that ismovable in a direction orthogonal to the surface of the photo-curableresin, and discharging new photo-curable resin onto a surface of eachcured layer formed on the movable stage before stacking a subsequentcured layer.

The optical molding method according to the aforementioned embodiment ofthe present invention may further include the step of ultrasonicallyvibrating the movable stage while the new photo-curable resin isdischarged.

The optical molding method according to the aforementioned embodiment ofthe present invention may further include the step of increasing ordecreasing a temperature at an end of the container while the newphoto-curable resin is discharged so as to create a convection currentin the photo-curable resin contained in the container.

The optical molding method according to the aforementioned embodiment ofthe present invention may further include the step of renewing thephoto-curable resin contained in the container before stacking thesubsequent cured layer.

According to the above embodiments of the present invention, each curedlayer is formed on the movable stage, which is movable in the directionorthogonal to the surface of the photo-curable resin contained in thecontainer, by emitting light onto the surface of the photo-curableresin. Moreover, new photo-curable resin is discharged onto the surfaceof each cured layer formed on the movable stage before stacking asubsequent cured layer.

Accordingly, the above embodiments of the present invention can achievethe capability to mold higher-precision three-dimensional models.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of an optical molding apparatus according toan embodiment of the present invention;

FIG. 2 illustrates a container and its surroundings, as viewed fromabove in FIG. 1;

FIGS. 3A and 3B illustrate the container and its surroundings, as viewedfrom the front in FIG. 1;

FIG. 4 illustrates a configuration example of an optical system shown inFIG. 1;

FIG. 5 is a block diagram showing a configuration example of hardware ofa control device that controls the individual units in the opticalmolding apparatus shown in FIG. 1;

FIG. 6 is a flow chart illustrating a molding process performed by a CPUshown in FIG. 5;

FIG. 7 is a flow chart illustrating a one-layer molding processperformed in step S17 in FIG. 6; and

FIG. 8 is an external view of an optical molding apparatus according toanother embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic external view of an optical molding apparatus 30according to an embodiment of the present invention.

The optical molding apparatus 30 in FIG. 1 includes an optical system 31having an objective lens 31A, an XY stage 32, a driving unit 33, acontainer 34, a glass window 35, ultraviolet curable resin 36 such asliquid resin, a valve 37, a nozzle 38, a YZ stage 39, and a driving unit40.

The optical molding apparatus 30 performs optical molding based on arestrained liquid-surface technique. Specifically, in this technique,the optical molding apparatus 30 uses the glass window 35 to restrainthe liquid surface of the ultraviolet curable resin 36 contained in thecontainer 34 and emits ultraviolet light to the ultraviolet curableresin 36 through the glass window 35 in accordance withcross-sectional-shape data. The term “liquid surface” of the ultravioletcurable resin 36 in this case refers to a surface of the ultravioletcurable resin 36 to which ultraviolet light is to be emitted.

In the optical molding apparatus 30, the optical system 31 is disposedon the XY stage 32 and has the objective lens 31A through which theultraviolet light is emitted to the ultraviolet curable resin 36. Theoptical system 31 performs exposure on predetermined rectangular areas(referred to as “small exposure areas” hereinafter) on the liquidsurface of the ultraviolet curable resin 36 on an area-by-area basis byemitting ultraviolet light according to cross-sectional-shape data ontoeach small exposure area on the liquid surface through the objectivelens 31A and the glass window 35. Specifically, these small exposureareas constitute an area of the liquid surface that is to define a shapeaccording to the cross-sectional-shape data.

The XY stage 32 can be moved in an x-axis direction and a y-axisdirection by the driving unit 33. The x-axis direction and the y-axisdirection are parallel to the liquid surface of the ultraviolet curableresin 36, and are orthogonal to each other.

Under the control of a control device 120 (FIG. 5) to be describedlater, the driving unit 33 sequentially moves the XY stage 32 by apredetermined distance in the x-axis direction so as to perform scanningon each of the small exposure areas in the x-axis direction.Subsequently, under the control of the control device 120, the drivingunit 33 moves the XY stage 32 by predetermined distances in the x-axisdirection and the y-axis direction, thus shifting the small exposureareas to a starting point of next one of scan lines arranged in they-axis direction. Then, under the control of the control device 120, thedriving unit 33 performs scanning again on each of the small exposureareas in the x-axis direction.

In this manner, the scan lines are sequentially scanned so that a workarea constituted by a predetermined number of small exposure areasarranged in the x-axis direction and the y-axis direction is exposed tolight in accordance with the cross-sectional-shape data. In consequence,the exposure is performed on the area of the ultraviolet curable resin36 that defines the shape corresponding to one layer's worth ofcross-sectional-shape data, thereby forming one cured layer 41 betweenthe glass window 35 and the YZ stage 39.

Accordingly, the optical molding apparatus 30 is configured to performexposure on the work area by having the small exposure areas arranged ina matrix, like tiles, in the x-axis direction and the y-axis direction.Therefore, in order to differentiate the optical molding method of theoptical molding apparatus 30 from a beam-scanning method or a one-shotexposure method of the related art, in which the small exposure areasand the work area are the same, the optical molding method of theoptical molding apparatus 30 will be referred to as a “tiling method”.

The container 34 is disposed above the objective lens 31A. The bottom ofthe container 34 is provided with the glass window 35. The container 34contains the ultraviolet curable resin 36. In FIG. 1, the inside of thecontainer 34 is shown in a see-through state for the sake ofconvenience.

The valve 37 is connected to the nozzle 38 having a plurality of holes38A, and controls the supply of ultraviolet curable resin 36 to thenozzle 38 under the control of the control device 120. The nozzle 38discharges new, externally-supplied ultraviolet curable resin 36 fromthe holes 38A. Consequently, when the cured layer 41 formed on the YZstage 39 is disposed above the nozzle 38, the ultraviolet curable resin36 near the surface of the cured layer 41 is circulated by newlydischarged ultraviolet curable resin 36, thereby removing uncured orsemi-cured ultraviolet curable resin 36 (referred to as “residual resin”hereinafter) adhered to the surface of the cured layer 41.

The YZ stage 39 is immersed in the ultraviolet curable resin 36contained in the container 34 and is movable in the y-axis direction anda z-axis direction under the control of the driving unit 40. The z-axisdirection is orthogonal to the liquid surface of the ultraviolet curableresin 36.

Every time an exposure process corresponding to one layer's worth ofcross-sectional-shape data is completed, the driving unit 40 moves theYZ stage 39 in the z-axis direction under the control of the controldevice 120 so as to separate the cured layer 41 formed between the glasswindow 35 and the YZ stage 39 from the glass window 35.

The driving unit 40 then moves the YZ stage 39 in the y-axis directionand the z-axis direction so as to dispose the cured layer 41 formed onthe YZ stage 39 to a position above the nozzle 38. As a result, theresidual resin is removed from the surface of the cured layer 41.

Subsequently, under the control of the control device 120, the drivingunit 40 returns the YZ stage 39 to the original position in the y-axisdirection and then moves the YZ stage 39 in the z-axis direction untilthe distance between the glass window 35 and the cured layer 41 isequivalent to the thickness of one cured layer. Accordingly, a new curedlayer can be stacked on the cured layer 41 from which the residual resinis removed. As a result, a high-precision three-dimensional model can bemolded.

Furthermore, while the nozzle 38 discharges ultraviolet curable resin 36therefrom, the driving unit 40 ultrasonically vibrates the YZ stage 39for a predetermined period of time under the control of the controldevice 120. This can facilitate the removal of residual resin by thenozzle 38.

The removal of residual resin performed in the optical molding apparatus30 in FIG. 1 will be described below with reference to FIGS. 2 and 3.

FIG. 2 illustrates the container 34 and its surroundings, as viewed fromabove in FIG. 1. FIGS. 3A and 3B schematically illustrate the container34 and its surroundings, as viewed from the front in FIG. 1.

Referring to FIG. 2, when the cured layer 41 is to be formed, the YZstage 39 is disposed at a predetermined position lower than that of thenozzle 38 having the plurality of holes 38A arranged at equally spacedintervals in an x-y plane. The optical system 31 performs exposure onthe ultraviolet curable resin 36 so as to form the cured layer 41between the YZ stage 39 and the glass window 35, as shown in FIG. 3A. Inthis case, a small amount of ultraviolet light enters regions notsubjected to exposure that are located near the regions subjected toexposure corresponding to the cured layer 41, causing residual resin 61to adhere to recesses in the surface of the cured layer 41, as shown inFIG. 3A. FIG. 3A only shows sections that are relevant to the formationof the cured layer 41.

When one cured layer 41 is formed, the YZ stage 39 moves in the z-axisdirection so as to separate the cured layer 41 from the glass window 35.The YZ stage 39 then moves in the y-axis direction and the z-axisdirection so that the cured layer 41 formed on the YZ stage 39 isdisposed above the nozzle 38, as shown in FIG. 3B. At this time, thevalve 37 controls the nozzle 38 such that the nozzle 38 dischargesexternally-supplied ultraviolet curable resin 36 from the holes 38A, andmoreover, the YZ stage 39 ultrasonically vibrates for a predeterminedperiod of time. In consequence, the residual resin 61 is removed fromthe surface of the cured layer 41. FIG. 3B only shows sections that arerelevant to the removal of the residual resin 61.

When the removal of the residual resin 61 is completed, the controldevice 120 performs control to open a valve 51A of an outlet pipe 51provided under the container 34, as shown in FIG. 2, thereby ejectingthe remaining ultraviolet curable resin 36, which was not used forforming the cured layer 41, in the container 34. Subsequently, thecontrol device 120 performs control to open a valve 52A of an inlet pipe52 provided above the container 34, as shown in FIG. 2, therebyinjecting an amount of ultraviolet curable resin 36 equivalent to onelayer into the container 34 for forming a subsequent cured layer.

In this manner, the optical molding apparatus 30 renews the ultravioletcurable resin 36 before stacking a subsequent cured layer. This canprevent the ultraviolet curable resin 36 from becoming semi-cured, whichcan occur if uncured ultraviolet curable resin 36 existing in regionsnot subjected to exposure and created during the previous formingprocess is exposed to ultraviolet light during the current formingprocess of a cured layer 41.

On the other hand, the YZ stage 39 moves in the y-axis direction toreturn to the original position, for forming the cured layer 41, in they-axis direction, and then moves in the z-axis direction until thedistance between the glass window 35 and the cured layer 41 isequivalent to one-layer's thickness of a subsequent cured layer to beformed. Subsequently, a new cured layer is formed by the optical system31 using the newly-injected ultraviolet curable resin 36 and is stackedon the previous cured layer 41. Then, the removal of residual resin andthe ejection and injection of ultraviolet curable resin 36 areperformed, as described above. By repeating these steps, cured layerswithout residual resin are stacked one on top of the other, whereby ahigh-precision three-dimensional model is molded.

FIG. 4 illustrates a configuration example of the optical system 31shown in FIG. 1.

The optical system 31 in FIG. 4 includes the objective lens 31A, aone-shot exposure optical system 71, a beam-scanning optical system 72,a polarization beam splitter 73, and a driving unit 74.

The one-shot exposure optical system 71 is configured to performone-shot exposure in which each small exposure area on the liquidsurface of the ultraviolet curable resin 36 contained in the container34 is exposed to light in one shot. The one-shot exposure optical system71 includes a light source 81, a shutter 82, a polarizing plate 83, abeam integrator 84, a mirror 85, a spatial light modulator 86, afocusing lens 87, and a driving unit 88.

The light source 81 may be of a type that has, for example, high-outputblue-light-emitting diodes (LEDs) arranged in an array. Unlike a lightsource 91 used for beam scanning, to be described later, it is notnecessary to use a coherent laser light source as the light source 81.Under the control of the control device 120, the light source 81 emitsultraviolet light to be used for performing the one-shot exposure.

Under the control of the control device 120, the shutter 82 controls theultraviolet light emitted from the light source 81 by transmitting orblocking the light, and also performs ON/OFF control of the exposureprocess performed by the one-shot exposure optical system 71.

The polarizing plate 83 polarizes the ultraviolet light passing throughthe shutter 82 so as to make the light into predetermined polarizedlight. Specifically, the polarizing plate 83 polarizes the ultravioletlight emitted from the light source 81 so that the spatial lightmodulator 86 can spatially modulate the light.

The beam integrator 84 uniformizes the ultraviolet light polarized bythe polarizing plate 83. The beam integrator 84 may be of a common type,such as a fly's eye type constituted by an array of multiple lenselements or a light rod type configured to cause the light to becompletely reflected within a rod lens having a columnar shape, e.g., arectangular columnar shape.

The mirror 85 reflects the ultraviolet light uniformized by the beamintegrator 84 towards the spatial light modulator 86.

The spatial light modulator 86 includes, for example, a transmissiveliquid crystal panel and spatially modulates a portion of theultraviolet light reflected by the mirror 85 so that the ultravioletlight can be projected on the small exposure areas on the liquid surfaceof the ultraviolet curable resin 36 on an area-by-area basis inaccordance with the cross-sectional-shape data.

Specifically, the spatial light modulator 86 receives a driving signal,for controlling each of pixels in the liquid crystal panel, from thecontrol device 120. Based on the driving signal, the spatial lightmodulator 86 changes the alignment of liquid crystal molecules in theindividual pixels in correspondence to an image of the shape accordingto the cross-sectional-shape data to be projected onto each of the smallexposure areas, so as to change the polarization direction of thetransmitted light, whereby the ultraviolet light passing through thespatial light modulator 86 is spatially modulated.

In consequence, the emission of ultraviolet light to each small exposurearea on the liquid surface of the ultraviolet curable resin 36 is turnedon and off for individual rectangular areas (referred to as “exposureunit areas” hereinafter) in that small exposure area in correspondenceto the shape set on a small-exposure-area by small-exposure-area basisaccording to the cross-sectional-shape data. In this case, each exposureunit area corresponds to one pixel of the liquid crystal panel. Theultraviolet light is emitted collectively to the exposure unit areas,which are subjected to receive the ultraviolet light, in each smallexposure area. Accordingly, each small exposure area on the liquidsurface of the ultraviolet curable resin 36 is exposed to theultraviolet light having the shape set on a small-exposure-area bysmall-exposure-area basis according to the cross-sectional-shape data.

Furthermore, as an alternative to the transmissive liquid crystal panel,the spatial light modulator 86 may include a digital micromirror device(DMD) having an array of reflective micromirrors, whose tilt angle isvariable in accordance with an input signal, or a reflectiveliquid-crystal-on-silicon (LCOS) device.

The focusing lens 87 is disposed between the spatial light modulator 86and the polarization beam splitter 73. Together with the objective lens31A, the focusing lens 87 functions as a projection optical system forforming an image of the ultraviolet light, spatially modulated by thespatial light modulator 86, on the ultraviolet curable resin 36.

The focusing lens 87 includes a lens group for correcting distortionthat may occur when the ultraviolet light spatially modulated by thespatial light modulator 86 passes through the objective lens 31A.Therefore, in addition to functioning as a projection optical system,the focusing lens 87 also has a function for reducing distortion.

For example, the lens group of the focusing lens 87 and a lens group ofthe objective lens 31A are arranged such that the focusing lens 87 andthe objective lens 31A are symmetrical optical systems. With thissymmetrical configuration, the ultraviolet light spatially modulated bythe spatial light modulator 86 can be focused on an anterior focal pointof the objective lens 31A located on a reflective-transmissive surface73A of the polarization beam splitter 73, thereby reducing distortion.

Under the control of the control device 120 based on feedback lightdetected by a reflective-light monitor unit 101 of the beam-scanningoptical system 72, to be described later, the driving unit 88 drives thespatial light modulator 86 in the z-axis direction, i.e., optical-axisdirection, so as to adjust the focus of the ultraviolet light emittedfrom the one-shot exposure optical system 71 towards the liquid surfaceof the ultraviolet curable resin 36.

The beam-scanning optical system 72 is configured to performbeam-scanning exposure by scanning a laser beam over each small exposurearea on the liquid surface of the ultraviolet curable resin 36 containedin the container 34. The beam-scanning optical system 72 includes alight source 91, a collimator lens 92, an anamorphic lens 93, a beamexpander 94, a beam splitter 95, a shutter 96, galvano mirrors 97 and98, relay lenses 99 and 100, and the aforementioned reflective-lightmonitor unit 101.

The light source 91 includes, for example, a semiconductor laser thatemits an ultraviolet laser light beam having a relatively shortwavelength between about the blue region and the ultraviolet region.Under the control of the control device 120, the light source 91 emitsan ultraviolet laser light beam to be used by the beam-scanning opticalsystem 72 for beam scanning. The light source 91 may be a gas laser asan alternative to the semiconductor laser.

The collimator lens 92 converts the angle of divergence of the lightbeam emitted from the light source 91 so as to substantially collimatethe light beam. The anamorphic lens 93 shapes the elliptical light beamsubstantially collimated by the collimator lens 92 so as to give thelight beam a substantially circular shape.

The beam expander 94 has a plurality of lenses and adjusts the beamdiameter of the light beam, given the substantially circular shape bythe anamorphic lens 93, by converting the beam diameter to a desiredbeam diameter suitable for, for example, the aperture and the numericalaperture of the objective lens 31A.

The beam splitter 95 transmits the light beam emitted from the lightsource 91 and causes the light beam to travel towards the ultravioletcurable resin 36 contained in the container 34. In addition, feedbacklight reflected by the ultraviolet curable resin 36 and then passingthrough the individual optical systems is reflected towards thereflective-light monitor unit 101 by the beam splitter 95.

Under the control of the control device 120, the shutter 96 controls thelight beam transmitted through the beam splitter 95 by transmitting orblocking the light beam so as to perform ON/OFF control of thebeam-scanning exposure performed by the beam-scanning optical system 72.Instead of performing the ON/OFF control of the beam-scanning exposureby transmitting or blocking the light beam using the shutter 96, theON/OFF control of the beam-scanning exposure may be performed bycontrolling direct modulation of the emission of the light beam in thelight source 91.

The galvano mirrors 97 and 98 each include a reflecting portion (notshown), such as a mirror, which is rotatable in a predetermineddirection and an adjusting portion (not shown) that adjusts the angle ofthe reflecting portion in the rotational direction in accordance withthe control performed by the control device 120. The adjusting portionadjusts the angle of the reflecting portion so that the light beamreflected by the reflecting portion can be scanned in the x-axisdirection or the y-axis direction within each small exposure area on theliquid surface of the ultraviolet curable resin 36.

Specifically, the galvano mirror 97 reflects the light beam transmittedthrough the shutter 96 towards the galvano mirror 98 and causes thelight beam to be scanned in the x-axis direction within each smallexposure area on the liquid surface of the ultraviolet curable resin 36.The galvano mirror 98 reflects the light beam reflected by the galvanomirror 97 towards the polarization beam splitter 73 and causes the lightbeam to be scanned in the y-axis direction across the liquid surface ofthe ultraviolet curable resin 36.

Alternatively, the galvano mirrors 97 and 98 in the optical system 31may be replaced by polygon mirrors.

The relay lenses 99 and 100 each include a lens group having one or morelenses. The relay lens 99 emits a collimated incident light beam in aparallel fashion over a scanning angle by which the light beam isscanned by the galvano mirror 97, and forms an image of the light beamreflected by the galvano mirror 97 on the galvano mirror 98. The relaylens 100 emits a collimated incident light beam in a parallel fashionover a scanning angle by which the light beam is scanned by the galvanomirror 98, and forms an image of the light beam reflected by the galvanomirror 98 on the reflective-transmissive surface 73A of the polarizationbeam splitter 73.

By providing the relay lens 99 between the galvano mirror 97 and thegalvano mirror 98 and providing the relay lens 100 between the galvanomirror 98 and the polarization beam splitter 73 in this manner, an imageof the light beam can be formed on the reflective-transmissive surface73A of the polarization beam splitter 73 even if the light beam isscanned by the galvano mirrors 97 and 98 that are not disposed adjacentto each other.

The reflective-light monitor unit 101 employs, for example, theastigmatic method or the triangulation method to detect the feedbacklight reflected by the liquid surface of the ultraviolet curable resin36, and inputs the detected result to the control device 120.

The polarization beam splitter 73 combines the ultraviolet light fromthe one-shot exposure optical system 71 with the light beam from thebeam-scanning optical system 72 and guides the combined light to theultraviolet curable resin 36. The polarization beam splitter 73 isdisposed such that the reflective-transmissive surface 73A thereofcoincides with the anterior focal point of the objective lens 31A.

The objective lens 31A includes a lens group having one or more lenses.The objective lens 31A forms an image of the ultraviolet light from theone-shot exposure optical system 71 on the liquid surface of theultraviolet curable resin 36, and also condenses the light beam from thebeam-scanning optical system 72.

Furthermore, the objective lens 31A is configured such that the lightbeam deflected by the galvano mirrors 97 and 98 in the beam-scanningoptical system 72 can be scanned at a uniform rate within each smallexposure area on the liquid surface of the ultraviolet curable resin 36,that is, scanned at a uniform scan-line rate on the liquid surface ofthe ultraviolet curable resin 36.

For example, the objective lens 31A is a so-called fθ lens that has animage height Y proportional to an incident angle θ and that has arelationship (Y=f×θ) in which the image height Y is equal to a productof a focal length f and the incident angle θ. In this case, the scanningrate of the light beam is constantly fixed regardless of the incidentposition of the light beam on the objective lens 31A. This can preventthe designed shape and the actual shape of a cured layer from beingdifferent from each other, which can occur due to variations in thescanning rate, thereby achieving high-precision molding.

Under the control of the control device 120 based on feedback lightdetected by the reflective-light monitor unit 101 of the beam-scanningoptical system 72, the driving unit 74 drives the objective lens 31A inthe z-axis direction so as to adjust the focus of the light beam emittedfrom the beam-scanning optical system 72 towards the liquid surface ofthe ultraviolet curable resin 36. In detail, the driving unit 74 drivesthe objective lens 31A in the z-axis direction so that a posterior focalpoint of the objective lens 31A coincides with the liquid surface of theultraviolet curable resin 36 contained in the container 34.

FIG. 5 illustrates a configuration example of hardware of the controldevice 120 that controls the individual units in the optical moldingapparatus 30 shown in FIG. 1.

In the control device 120 shown in FIG. 5, a central processing unit(CPU) 121, a read-only memory (ROM) 122, and a random-access memory(RAM) 123 are mutually connected to one another via a bus 124.

The bus 124 is further connected to an input/output interface 125. Theinput/output interface 125 is connected to an input unit 126 includingfor example, a keyboard, a mouse, and a microphone, to an output unit127, including, for example, a display and a speaker, to a storage unit128 including, for example, a hard disk and a nonvolatile memory, to acommunication unit 129 including, for example, a network interface andcommunicable with the optical molding apparatus 30, and to a drive 130that drives a removable medium 131, such as a magnetic disc, an opticaldisc, a magneto-optical disc, or a semiconductor memory.

The storage unit 128 stores, for example, a program for convertingthree-dimensional-shape data of a three-dimensional model created bycomputer aided design (CAD) to stereo lithography (STL), which is aformat that expresses the surface of the three-dimensional model withsmall triangular surfaces, a program for creating cross-sectional-shapedata of the three-dimensional model from the STL-convertedthree-dimensional-shape data, and a program for controlling the one-shotexposure optical system 71 and the beam-scanning optical system 72 onthe basis of the cross-sectional-shape data of the three-dimensionalmodel.

In the control device 120, the CPU 121 loads, for example, the programsstored in the storage unit 128 into the RAM 123 via the input/outputinterface 125 and the bus 124 so as to execute the programs, andcontrols the individual units in the optical molding apparatus 30 viathe communication unit 129 so as to cause the optical molding apparatus30 to perform optical molding.

For example, the CPU 121 in the control device 120 determines theintensity of ultraviolet light to be emitted from the light source 81 orthe light source 91 in accordance with an input from the input unit 126,and sends a control signal for controlling the intensity to the lightsource 81 or the light source 91 via the communication unit 129. Inaccordance with an input from the input unit 126, the CPU 121 sends acontrol signal used for performing ON/OFF control of an exposure processto the shutter 82 or the shutter 96 via the communication unit 129.

Furthermore, in accordance with the cross-sectional-shape data, the CPU121 sends a driving signal for controlling the individual pixels in theliquid crystal panel to the spatial light modulator 86 via thecommunication unit 129 so that an image of the shape set on asmall-exposure-area by small-exposure-area basis according to thecross-sectional-shape data is displayed.

Moreover, based on feedback light received from the reflective-lightmonitor unit 101 via the communication unit 129, the CPU 121 sends acontrol signal for driving the spatial light modulator 86 in the z-axisdirection to the driving unit 88 via the communication unit 129 and alsosends a control signal for driving the objective lens 31A in the z-axisdirection to the driving unit 74 via the communication unit 129.

Furthermore, in accordance with the cross-sectional-shape data, the CPU121 sends a control signal for adjusting the angle of the reflectingportions of the galvano mirrors 97 and 98 to the galvano mirrors 97 and98 via the communication unit 129 so that an exposure process related tothe shape set on a small-exposure-area by small-exposure-area basisaccording to the cross-sectional-shape data is performed.

Furthermore, the CPU 121 sends a control signal for moving the XY stage32 in the x-axis direction by a predetermined distance at apredetermined timing to the driving unit 33 via the communication unit129 so that each of the small exposure areas can be scanned in thex-axis direction. When the scanning of each of the small exposure areasin the x-axis direction is completed, the CPU 121 sends to the drivingunit 33 via the communication unit 129 a control signal for shifting thesmall exposure areas to a starting point for a subsequent scan line.

Every time an exposure process corresponding to one layer's worth ofcross-sectional-shape data is completed, the CPU 121 sends a controlsignal for moving the YZ stage 39 by a predetermined distance in thez-axis direction to the driving unit 40 via the communication unit 129.This separates the cured layer 41 formed between the glass window 35 andthe YZ stage 39 from the glass window 35. Subsequently, the CPU 121sends to the driving unit 40 via the communication unit 129 a controlsignal for moving the YZ stage 39 with the cured layer formed thereon toa position above the nozzle 38. The CPU 121 then sends to the drivingunit 40 via the communication unit 129 a control signal for returningthe YZ stage 39 to the original position in the y-axis direction and formoving the YZ stage 39 in the z-axis direction such that the distancebetween the glass window 35 and the formed cured layer 41 becomesequivalent to the thickness of one cured layer to be formed in thesubsequent process.

Furthermore, at a predetermined timing, the CPU 121 sends a controlsignal for opening the valve 37 to the valve 37 via the communicationunit 129 and also sends a control signal for ultrasonically vibratingthe YZ stage 39 to the driving unit 40 via the communication unit 129.Moreover, the CPU 121 sends a control signal for opening the valve 51Aor 52A shown in FIG. 2 to the valve 51A or 52A via the communicationunit 129.

A molding process performed by the CPU 121 in FIG. 5 will now bedescribed with reference to FIG. 6. This molding process starts inresponse to, for example, an instruction for molding input to the inputunit 126 by the user.

In step S11, the CPU 121 selects three-dimensional-shape data of athree-dimensional model, designated by the user in accordance with aninput from the input unit 126, as three-dimensional-shape data of athree-dimensional model to be molded. The CPU 121 then createscross-sectional-shape data from the three-dimensional-shape data.

In step S12, the CPU 121 performs an initial setting process. In detail,for example, the CPU 121 controls the driving units 33 and 40 so as tomove the XY stage 32 and the YZ stage 39 to initial positions. Moreover,the CPU 121 sends control signals for controlling the intensities ofultraviolet light and light beam to the light sources 81 and 91,respectively, and measures the intensities of the ultraviolet light andthe light beam emitted respectively from the light sources 81 and 91 incorrespondence to the control signals. Furthermore, the CPU 121 opensthe valve 52A in FIG. 2 for a predetermined period of time so thatultraviolet curable resin 36 necessary for forming one cured layer isinjected into the container 34.

In step S13, the CPU 121 controls the driving units 33 and 40 so as tomove the XY stage 32 and the YZ stage 39 to preliminarily set startingpositions for molding. In step S14, the CPU 121 controls the drivingunit 40 so as to slowly move the YZ stage 39 downward in the z-axisdirection.

In step S15, the CPU 121 controls the driving unit 40 so as to stop theYZ stage 39 at a position near the top surface of the glass window 35.

In step S16, the CPU 121 controls the driving unit 40 so as to move theYZ stage 39 upward by a distance equivalent to the thickness of onecured layer 41 to be formed first. In step S17, the CPU 121 performs aone-layer molding process for molding one cured layer. This one-layermolding process will be described in detail later with reference to aflow chart in FIG. 7.

In step S18, the CPU 121 controls the driving unit 40 so as to move theYZ stage 39 upward by a predetermined distance in the z-axis direction.In consequence, the cured layer formed between the glass window 35 andthe YZ stage 39 is separated from the glass window 35.

In step S19, the CPU 121 controls the driving unit 40 so as to move theYZ stage 39 by a predetermined distance in the y-axis direction and thez-axis direction until the cured layer formed on the YZ stage 39 isdisposed above the nozzle 38. In step S20, the CPU 121 controls thevalve 37 so as to supply ultraviolet curable resin 36 to the nozzle 38for a predetermined period of time, thus causing the nozzle 38 todischarge the ultraviolet curable resin 36 therefrom for thepredetermined period of time. At the same time, the CPU 121 controls thedriving unit 40 so as to ultrasonically vibrate the YZ stage 39 for apredetermined period of time. In consequence, residual resin adhered tothe surface of the cured layer is removed from the surface.

In step S21, the CPU 121 controls the valve 51A (FIG. 2) so as to openthe valve 51A for a predetermined period of time, whereby theultraviolet curable resin 36 remaining in the container 34 is ejectedoutward from the outlet pipe 51.

In step S22, the CPU 121 determines whether to terminate the stackingprocess, that is, determines whether the process in step S17 isperformed for the number of layers corresponding to thethree-dimensional-shape data selected in step S11. If it is determinedin step S22 that the stacking process is not to be terminated, that is,if a three-dimensional model having the shape corresponding to thethree-dimensional-shape data selected in step S11 is not completelymolded yet, the CPU 121 controls the valve 52A in step S23 to open thevalve 52A for a predetermined period of time so that an amount ofultraviolet curable resin 36 necessary for forming one cured layer isinjected into the container 34 through the inlet pipe 52.

In step S24, the CPU 121 controls the driving unit 33 so as to move theXY stage 32 again to the starting position for molding. In step S25, theCPU 121 controls the driving unit 40 so as to move the YZ stage 39 inthe z-axis direction until the distance between the top surface of theglass window 35 and the bottom surface of the cured layer formed on theYZ stage 39 is equivalent to the thickness of one cured layer to beformed next. The process then returns to step S17, and the series ofsteps S17 to S25 is repeated until the CPU 121 determines to terminatethe stacking process. Accordingly, cured layers are stacked in thismanner.

On the other hand, if the CPU 121 determines to terminate the stackingprocess in step S22, that is, if the CPU 121 determines that athree-dimensional model having the shape corresponding to thethree-dimensional-shape data selected in step S11 is completely molded,the CPU 121 controls the driving units 33 and 40 in step S26 so as tomove the XY stage 32 and the YZ stage 39 to the initial positions,thereby ending the process.

The one-layer molding process performed in step S17 in FIG. 6 will nowbe described with reference to FIG. 7.

In step S41, the CPU 121 controls the individual units so as performexposure on the small exposure areas on the liquid surface of theultraviolet curable resin 36 contained in the container 34 on anarea-by-area basis by using the ultraviolet light from the one-shotexposure optical system 71 or the light beam from the beam-scanningoptical system 72. In step S42, the CPU 121 determines whether step S41is repeated by a predetermined number of times (e.g. the number of smallexposure areas arranged in the x-axis direction within the work area).

If it is determined in step S42 that step S41 is not repeated by thepredetermined number of times, the CPU 121 sends a control signal to thedriving unit 33 in step S43 so as to move the XY stage 32 in the x-axisdirection by a distance equivalent to the length of one small exposurearea in the x-axis direction. The process then returns to step S41, andthe series of steps S41 to S43 is repeated until step S41 is repeated bythe predetermined number of times.

On the other hand, if it is determined in step S42 that step S41 isrepeated by the predetermined number of times, that is, if the scanningof each of the small exposure areas in the x-axis direction iscompleted, the CPU 121 sends a control signal to the driving unit 33 instep S44 so as to move the XY stage 32 to the starting position in thex-axis direction.

In step S45, the CPU 121 sends a control signal to the driving unit 33so as to move the XY stage 32 in the y-axis direction by a distanceequivalent to the length of one small exposure area in the y-axisdirection. As the result of steps S44 and S45, the small exposure areasare shifted to a starting position for a subsequent scan line.

In step S46, the CPU 121 controls the individual units so as performexposure on the small exposure areas on the liquid surface of theultraviolet curable resin 36 contained in the container 34 on anarea-by-area basis.

In step S47, the CPU 121 determines whether step S46 is repeated by apredetermined number of times (e.g. the number of small exposure areasarranged in the y-axis direction within the work area). If it isdetermined in step S47 that step S46 is not yet repeated by thepredetermined number of times, the process proceeds to step S48 wherethe CPU 121 sends a control signal to the driving unit 33 so as to movethe XY stage 32 in the x-axis direction by a distance equivalent to thelength of one small exposure area in the x-axis direction. The processthen returns to step S41 where exposure is performed on the smallexposure areas on an area-by-area basis. Subsequently, the processproceeds to step S42.

At this time, in step S42, it is determined whether step S41 is repeatedby a predetermined number of times (e.g. a number obtained bysubtracting 1 from the number of small exposure areas arranged in thex-axis direction within the work area), and the series of steps S41 toS43 is repeated until step S41 is repeated by the predetermined numberof times. Subsequently, steps S44 to S46 are performed, and the seriesof steps S41 to S48 is similarly repeated until step S46 is repeated bythe predetermined number of times.

On the other hand, if it is determined in step S47 that step S46 isrepeated by the predetermined number of times, that is, if exposure isperformed on an area defining the shape corresponding to one-layer'sworth of cross-sectional-shape data, the process returns to step S17 inFIG. 6.

Accordingly, in the optical molding apparatus 30, residual resin adheredto the surface of a current cured layer formed on the YZ stage 39 isremoved before stacking a subsequent cured layer, whereby the subsequentcured layer can be stacked on the current cured layer from which theresidual resin is removed. As a result, a high-precisionthree-dimensional model can be molded.

Referring to FIG. 8 showing another embodiment of the present invention,the optical molding apparatus 30 may be equipped with a temperatureadjusting mechanism 201 configured to increase or decrease thetemperature at an end of the container 34. In that case, under thecontrol of the control device 120, the temperature adjusting mechanism201 increases or decreases the temperature at the end of the container34 while the nozzle 38 discharges ultraviolet curable resin 36therefrom. This creates a convection current in the ultraviolet curableresin 36 within the container 34, thereby facilitating the removal ofresidual resin by the nozzle 38.

Although the nozzle 38 is provided within the container 34 according tothe above description, the nozzle 38 may be provided in anothercontainer that is independent of the container 34.

Furthermore, the optical molding apparatus 30 may be provided with adriving unit that moves the nozzle 38 within the x-y plane. In thatcase, the ultraviolet curable resin 36 can be discharged over the entiresurface of a cured layer at small intervals even if the nozzle 38 hasonly a small number of holes 38A or has a small size in the x-y plane.Consequently, the removal of residual resin can be properly performed.

The above embodiments of the present invention have a remarkable effectespecially when molding a three-dimensional model having a small size inthe order of micrometers.

Furthermore, in addition to the above-described optical moldingapparatus that performs optical molding based on a tiling method,another embodiment of the present invention may provide an opticalmolding apparatus that performs optical molding based on a one-shotexposure method or a beam-scanning method. Furthermore, in addition tothe above-described optical molding apparatus that performs opticalmolding based on a restrained liquid-surface technique, anotherembodiment of the present invention may provide an optical moldingapparatus that performs optical molding based on a free liquid-surfacetechnique.

In this specification, the steps written in the program stored in aprogram recording medium may be performed in a time-series fashionaccording to the above-written order, or may be performed in a parallelfashion or in an individual fashion, instead of being performed in thetime-series fashion.

The embodiments of the present invention are not limited to theabove-described embodiments, and various modifications are permissibleto an extent that they do not depart from the scope of the invention.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An optical molding method performed by an optical molding apparatusthat molds a three-dimensional model by stacking cured layers, eachcured layer being formed by emitting light according tocross-sectional-shape data of the three-dimensional model onto a surfaceof photo-curable resin, the method comprising the steps of: emitting thelight onto the surface of the photo-curable resin contained in acontainer so as to form each cured layer on a movable stage that ismovable in a direction orthogonal to the surface of the photo-curableresin; and discharging new photo-curable resin onto a surface of eachcured layer formed on the movable stage before stacking a subsequentcured layer.
 2. The optical molding method according to claim 1, furthercomprising the step of ultrasonically vibrating the movable stage whilethe new photo-curable resin is discharged.
 3. The optical molding methodaccording to claim 1, further comprising the step of increasing ordecreasing a temperature at an end of the container while the newphoto-curable resin is discharged so as to create a convection currentin the photo-curable resin contained in the container.
 4. The opticalmolding method according to claim 1, further comprising the step ofrenewing the photo-curable resin contained in the container beforestacking the subsequent cured layer.